Close-up of aluminium coil fins, half clogged with grey dust and half clean — AI-generated picture. Half clean, half clogged. Air passes through these fins, so the dust travels with it.

Stories / Outside the window / story 9 of 18

The dust you can't see from the room

Dirty AC coils in a dusty city reduce cooling and raise electricity use, and while a homeowner can keep filters clean, washing the indoor and outdoor coils is a job for a technician.

From The AC in Your Flat. Updated 4 November 2026.

Filters protect the indoor coil, but nothing stops road dust reaching the outdoor unit. Daikin's maintenance page says cleaning the heat exchanger behind the filter also helps keep electricity use low. Check it before the cooling season, and if dirt is noticeable, contact your dealer.

How do you know the coil is dirty?

A filter you can lift out; a coil you only see in part. Clues are a cooling drop you can't explain, a longer time to cool the room and a bill jumping without a change in use. Daikin puts dirty coils, low refrigerant and worn parts among the causes. It's not always the coil, which is why the visit should include a check rather than a guess.

A dusty road in Thane East with auto-rickshaws around a flyover pillar, and flats with outdoor units behind — Thane East: flyover works and traffic. Units at this level breathe the road.

A cyclist on a wide Pune road with flats and shops under trees — Pune, on a dry day. Dry months bring dust, and the first rains turn it to mud on the fins.

Why not wash it yourself?

Because the inside of an AC is full of electrics and thin fins. Daikin says no shop-bought sprays, and it notes these can cause water leaks. Outdoors, the rule on reaching the unit applies. A technician should cover the board and electrics, and catch the water.

A Pune road crossing with a cyclist, a tin-roofed market and tall flats behind — Traffic, markets, construction. All of it ends up on the fins, and a few weeks can show it.

How often should coils be cleaned?

Daikin's general advice is a service once a year, just before the cooling season, and twice a year where the AC runs almost non-stop in hot or humid places. Many flats in Mumbai or Chennai may fall in the second group. Ask the technician to show you the coil before and after, so you can judge your own building.

Yellow office and shop buildings in Ameerpet, Hyderabad, seen from a raised metro line with a red roof below — Hyderabad's Ameerpet from the metro. Cities differ, but dusty air is common to all of them.

What to do

Yours to do

Keep the filter clean so the indoor coil stays cleaner for longer.
Keep stored items away from any unit you can walk up to.
Note when cooling dropped and any building work nearby, then tell the technician.

Leave to the trained person

Washing indoor and outdoor coils, with electrics protected and water caught.
Straightening damaged fins, if needed.

Also asked

Is a "jet service" necessary every time?

Not necessarily. Daikin's description of a service covers filters, coils, refrigerant level, electrical checks and a test run, and it doesn't call for a pressure jet each visit. Ask why it's needed and what it will be pointed at.

Can dust cause a fire?

A Business Today explainer says dust-clogged filters and dirty coils reduce airflow and make the system overheat, and it lists poor maintenance among the causes of AC fires. Such fires are rare, and a clean unit is part of the answer.

Where this came from

Daikin, maintenance tips: Coil and electricity use
Daikin Middle East and Africa, how often to service: Service interval and warning signs
Daikin, troubleshooting: Sprays
Business Today, 29 May 2026: Overheating and maintenance

This story rests on those pages, opened or checked by 4 November 2026, and on no tests of our own. Maker pages speak for their makers, and rules and wiring differ by building, so check your own manual.